Blood Vessel Flashcards
3 types of blood vessels
- arteries
- capillaries
- veins
Which of these vessels is the site of exchange between blood and interstitial fluid?
capillaries
what is getting exchanged in the capillaries
O2, CO2, nutrients, hormones, and waste are exchanged between blood and interstitial fluid
Arteries
- carry blood away from the heart
- arteries branch into arterioles which feed into the capillary beds of the body’s tissues and organs
- systemic circulation, arteries carry oxygen-rich blood
Veins
- return blood to the heart
- from capillary beds, blood drains into venules which then converge into larger veins until they return to the heart
- systemic circulation, veins carry oxygen-poor blood
What important role do lymphatic vessels play?
recovers the fluid that leaks from the blood vessels
3 layers of each blood vessel wall from deepest to most superficial
- tunica externa
- tunica Media
- tunica intima
tunica intima
innermost layer, contacts the passing blood
- endothelium is continuous with endocardial lining of the heart
- in vessels larger than 1mm in diameter - a subendothelial layer supports the tunica intima
tunica media
middle layer, circularly arranged smooth muscle cells and sheets of elastin
- more robust in arteries
- activity of the smooth muscle is regulated by sympathetic vasomotor nerve fibers and chemicals
- small changes in Vessel diameter greatly influence blood flow and blood pressure
tunica externa
loosely woven collagen fibers that protect, reinforce, and anchor the vessel
- infiltrated by nerve fibers, lymphatic vessels, and a network of elastin fibers
- in larger vessels, the tunica externa contains vasa vasorum - a network of tiny blood vessels that nourish the vessel itself
3 types of arteries
- Elastic arteries
- Muscular arteries
- Arterioles
Elastic Arteries
- thick walled arteries near the heart - aorta and its major branches
- large diameter - 1 to 2.5 cm
- elastin present in all three tunica, but tunica Media contains the most
- despite smooth muscle, relatively inactive as vasoconstrictors
- act as pressure reservoirs - expand/recoil as the heart ejects blood
- “smooth” pressure and make blood flow fairly continuously - protection for smaller arteries
Muscular Arteries
- distal to elastic arteries
- deliver blood to specific body tissues/organs
- most named arteries are muscular arteries (brachial, radial)
- diameteres range from the size of a pencil lead to a little finger
- proportionate to their size, muscular arteries have the thickest tunica media
arterioles
- smallest arteries
- larger arterioles have all three tunica - the tunica media is chiefly smooth muscle with minimal elastin
- smaller arterioles are largely a single layer of smooth muscle around the endothelial lining
- diameter varies in response to neural, hormonal, and local chemical influences
What tissues do NOT have a rich capillary supply?
tendons, ligaments, cartilage, and epithelia
3 types of capillaries
- continuous
- fenestrated
- sinusoid
continuous capillary
most common, least permeable
- abundant in skin, muscles, lungs, and CNS
Fenestrated capillary
large fenestrations or pores increases permeability
- abundant in kidneys, small intestine, and area of hormone
sinusoid capillary
occur in limited locations, the most permeable
- found in liver, bone marrow, spleen and adrenal medulla
intercellular clefts
gaps of un-joined membrane
microcirculation
how blood flows from an arteriole to a venule through a capillary bed
terminal arteriole
branches into 10-20 capillaries - capillary bed
vascular shunt
a vessel that directly connects the terminal arterioles to the postcapillary venule - allows blood to bypass the true capillaries
metarteriole
shunt consists of a metarteriole and a thoroughfare channel
